Effect of Annealing Temperature on the Microstructural Evolution and Mechanical Properties of AISI 631 Strip

This study systematically investigated the effects of annealing temperature (750°C–1050°C) on the microstructural evolution and mechanical properties of AISI 631 stainless steel thin strips for bearing applications. Microstructural characterization was performed using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD), while mechanical properties were evaluated via three‐point bending tests, Vickers hardness measurements, and tensile testing. At annealing temperatures below 950°C, Cr‐rich M23C6 carbides precipitated along grain boundaries and within grains, effectively pinning grain boundaries. With increasing annealing temperature, both the fraction of low‐angle grain boundaries (LAGBs) and the Kernel Average Misorientation (KAM) decreased. The variant was identified as the dominant martensitic variant following annealing at 750°C. Microhardness and tensile strength progressively decreased with rising annealing temperature, while three‐point bending tests indicated that the springback angle diminished with increasing grain size. These findings provide new insights into the interplay among microstructure, crystallographic orientation, and bending behavior in AISI 631 strips, offering a theoretical foundation for optimizing heat‐treatment processes.